This invention relates to apparatus for facilitating the transmission of voice and data across a Local Area Network (LAN) and, more particularly, to a port prioritizing device which gives priority to voice-containing packets, over data packets, to ensure high voice quality transmission over the LAN.
A variety of approaches have been explored throughout the telephone and data networking industries for carrying telephone communications across Local Area Networks (LAN""s). Widespread deployment of such telephone systems, though, has been slow for a variety of reasons, including concerns about voice quality. One key component of the voice quality issue is the timely delivery of voice-containing packets across an LAN. Timely delivery of voice-containing packets results from the problem of contention between voice frames and data frames originating in the endpoint.
Traditional voice telephone is based on the guaranteed timely arrival of each successive voice sample at the listening endpoint. Dedicated channels through the existing STM network are designed to support just such timely transport of the voice traffic. LAN networks, on the other hand, share a common channel among many endpoints, providing access to potentially greater amounts of bandwidth at the expense of guaranteed timely access. While this is an excellent compromise for near-real-time applications such as file transfer, World Wide Web access, etc., when applied to real-time applications like voice communications, the resulting performance is poor, with drop-outs and distortion in the received voice stream.
As the data networking world advances, network ports are becoming less and less expensive. Dedicated switched ports will soon cost as little as shared ports did just a few years ago, and will be competitive with the cost of telephone ports. With dedicated switched Ethernet, much of the real-time data quality problem lies in the sharing of the network port between the real-time applications (i.e., voice) and the non-real-time applications.
Various proposals to establish a priority mechanism for Ethernet LAN""s have been put forth in the prior art. These approaches attempt to provide a higher priority for the real-time data, with thus a slight advantage over the non-real-time data. These approaches, however, necessitate modifying the computer workstation, either by installing new hardware or software, which is a disadvantage both in terms of cost and the time necessary to retrofit the computer workstation.
It is, therefore, an object of this invention to provide high quality voice transmission over a data network, such as a LAN, without the necessity to retrofit computer work stations associated with the LAN.
It is a further object of this invention to provide high quality voice transmission over a data network, such as a LAN, without disrupting the flow of data between the associated work stations.
It is a still further object of this invention to provide a simple and inexpensive device, easily connected to a data network, which allows high quality voice transmission over the data network without disrupting the flow of data.
In accordance with this invention, the aforementioned deficiencies are addressed and improvement is made in the art by the provision of a Port Prioritizing Device (PPD) that interfaces a computer device and a telecommunications terminal device, such as, for example, a telephone, with a data network that is typically used exclusively for carrying data associated with computer devices.
According to the present invention, the port prioritizing device is powered independently from the computer device. It accepts packetized data from each interface, and merges those data and sends them out to the data network. In doing so, the device provides a higher priority for packets from the telecommunications device, by blocking the transmission of computer packets while telecommunications packets are being sent. The invention is particularly unique in that its proper operation does not depend on changes in design of existing computer network equipment such as Network Interface Cards (NICs), hubs, or switches.
It is a feature of the invention that blocking transmission of computer packets is accomplished by transmitting real-time packets (i.e., voice) to both the network and the data endpoint, so that the data endpoint will think that the network is busy.
It is a further feature of the invention that real-time data packets are given priority without the necessity of examining bits in each data packet to determine priority.
The foregoing and other objects and features of this invention will be more fully understood from the following description of an illustrated embodiment thereof taken in conjunction with the accompanying drawings.